Need some guidance before I pull the trigger

[bradley.r.zeller]

Awesome, thanks for confirming my thinking!

Of course, it does defeat the "visible blade" feature of the disconnect before inverter, because invisible internal fault would go around and back to grid. But go for it, same as any generator interlock in a panel.

Can you explain this one a bit more? Not sure I follow.

If inverter supports 200A pass-through (or 125A), when grid drops inverter is overloaded and shuts down, unless automatic load-shed. Interlocked breakers lets you manually shed big loads.

This is probably ignorance on my part but I’ve attempted to add up a realistic (but unlikely) max load that I could pull from the panel at any given time and it’s just barely over the 12kw / 50a continuous output rating of this inverter. Because of the unlikeliness of this scenario (grid down while attempting to pull beyond 12kw) and because the inverter is rated for some solid surge output for 10-15m, I’m thinking I could get away w/o a critical loads panel. And if needed, manually load shed certain things if the situation arose.

Is this unwise? My thinking is that a critical loads panel will limit my self consumption and thus extend the ROI of this investment (e.g. if I place 50% of all my loads in the critical loads panel, the inverter could only ever offset 50% of my power consumption). In my head it makes more sense to have all loads downstream of the inverter, allow the inverter to provide as much as it can and utilize the grid blend feature to supplement the rest of my consumption from the grid (in the cases where I exceed the inverter). I think the only downside is the possibility of “manually” load shedding things in the case that the grid goes down… am I thinking about this right?

 

[Hedges]

Awesome, thanks for confirming my thinking!


Can you explain this one a bit more? Not sure I follow.

Utility asked for a visible blade switch, which absolutely, positively, isolates inverter from grid. Not just a breaker.

The generator interlock is just a breaker between inverter and grid.

This is probably ignorance on my part but I’ve attempted to add up a realistic (but unlikely) max load that I could pull from the panel at any given time and it’s just barely over the 12kw / 50a continuous output rating of this inverter. Because of the unlikeliness of this scenario (grid down while attempting to pull beyond 12kw) and because the inverter is rated for some solid surge output for 10-15m, I’m thinking I could get away w/o a critical loads panel. And if needed, manually load shed certain things if the situation arose.

Is this unwise? My thinking is that a critical loads panel will limit my self consumption and thus extend the ROI of this investment (e.g. if I place 50% of all my loads in the critical loads panel, the inverter could only ever offset 50% of my power consumption). In my head it makes more sense to have all loads downstream of the inverter, allow the inverter to provide as much as it can and utilize the grid blend feature to supplement the rest of my consumption from the grid (in the cases where I exceed the inverter). I think the only downside is the possibility of “manually” load shedding things in the case that the grid goes down… am I thinking about this right?

So you're probably fine in terms of inverter wattage.
Maybe not battery Wh capacity. For instance, I can have a 10kW electric duct heater on. My 23kW of inverters have no trouble with that, but at 0.5C discharge rate and Peukert, will reach 70% DoD in about one hour.

So it is useful to have an SoC based load-shed. While sun is out you can run big loads, probably not for long at night.

I want to load-shed the electric heater (switch back to gas) when off grid, shed the dryer when battery not near full. Or hardwire those straight to grid.

For now I load shed the entire house at 70% DoD. Would be nice to have communications on critical loads panel which would remain up.

 

[zanydroid]

Circling back to the 100A main breaker and a single 100A breaker that is tapped to feed both inverter and panel… you said this:

This is also called 100% rule (and maybe also hawaii tie-in?)

And as another vote of support for it. I passed PTO with PG&E twice with this setup. Currently I have 90A of solar backfeed breakers going through a 100A panel set up this way. System is like 17kW-AC

1) the manual transfer switch - this switch is over $1000 at Lowes. Instead of a standalone transfer switch, could I not accomplish the same function (and remain code compliant) by connecting both grid and inverter output to the main panel directly (each on their own 125a breaker), and interlock them so only one can be on at a time? This seems much simpler and cost effective.

The beauty of 100A is it doesn't have to cost $1000.

You can get 100A 3 position switch (ON-OFF-ON) for close to or cheaper than dedicated breaker interlock and panels. If you can make the interlock work out with existing subpanels and main panels it will be slightly cheaper and smaller.

Functionally I believe interlock plates can do exactly the same thing as ON-OFF-ON

 

[zanydroid]

IMHO the blade switch that is standard in a lot of interconnection applications and SLDs is IMO there to maximize the number of POCO and AHJ that a cookie cutter plan is good for.

My town (and PG&E) doesn't require one for my system (microinverters). Dunno about ESS or string (string or inverter shouldn't matter to the AC side)

 

[ricardocello]

You can get 100A 3 position switch (ON-OFF-ON) for close to or cheaper than dedicated breaker interlock and panels.

UL Listed?

 

[zanydroid]

UL Listed?

Doesn't this look legit? $200

Now price out 2 100A breakers and a subpanel

https://www.amazon.com/Eaton-240-Volt-Non-Fused-General-Duty-Double-Throw/dp/B008KNXJXE/ref=asc_df_B008KNXJXE/?tag=hyprod-20&linkCode=df0&hvadid=309768150198&hvpos=&hvnetw=g&hvrand=4011329425267930143&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031914&hvtargid=pla-647079725925&psc=1&mcid=2a8220f4c38036358bc5a57f2fdaa90b&gclid=Cj0KCQjwlN6wBhCcARIsAKZvD5i9otBKvBvUbViHKxB6clhtxifNH2qrJqehU0P-RaVJ2Bwli0nKnogaAi58EALw_wcB

Maybe there are fusible/service rated ones too, that will allow a neater install in some ways too

Sometimes I feel like 200A bypass/passthrough is a "scam"

 

[ricardocello]

Doesn't this look legit? $200

Super legit, excellent find.

I went with two subpanels and interlocks.

 

[ricardocello]

Amazon, wtf? x-10?

 

[Hedges]

Nothing in the photos indicates support for that.

Somebody defined fields. Usually says "no", like a 9V battery from Radio Shack didn't support WiFi connectivity.

Relying on hired help ...

(I didn't even see what you saw, until I used down arrow for "more")

 

[zanydroid]

X10 pages the ghost to come in and pull the switch for you.

Since I don't see any actuators in there.

 

[ricardocello]

X10 pages the ghost to come in and pull the switch for you.

Since I don't see any actuators in there.

I used to have x-10 appliance modules that had a relay that made a really loud click.
I got a good chuckle thinking how loud it would be with that thing.

 

[zanydroid]

You can probably put your own big ass solenoid on the outside and throw the switch that way.

 

[bradley.r.zeller]

Thanks everyone, I'm learning a ton here.

So it is useful to have an SoC based load-shed. While sun is out you can run big loads, probably not for long at night.

@Hedges - Can your system automatically shed loads based on SOC? If so, what type of equipment supports that? A smart panel type thing?

The beauty of 100A is it doesn't have to cost $1000.

@zanydroid - But if I had a 125A main breaker, I'd need a 125A transfer switch right? I can't find any 125A transfer switches anywhere - maybe they don't make them? Looks like I'd have to go up to a 200A switch...

I think I've almost wrapped my head entirely around what this install will look like. Can ya'll shed any advice on the following equipment I plan to install? For context, I am replacing my ground fed 100A meter / load center box. Also, it's tough finding 125A rated equipment, so some of these things are rated for 125A (if there's a way around going all the way up to 200A, let me know! 200A rated equipment is pricey).

1. Install this stand-alone meter + breaker where the utility feeders enter my wall
2. In the breaker area of the meter box, I'd tap the conductors with three of these 2/0 AWG taps
3. From the taps...
   1. One set of the conductors would feed a transfer switch like this.
   2. One set of conductors would feed into a disconnect switch like this. From here, I'd connect to the inverter's grid connection. The inverter's load connection would be feed the other side of the transfer switch above.
4. The transfer switch output would then feed my whole house 200A load center like this.
5. The conductors between each of this equipment would be 2/0 AWG.

Thanks ya'll!

 

[Hedges]

@Hedges - Can your system automatically shed loads based on SOC? If so, what type of equipment supports that? A smart panel type thing?

My system has multiple Sunny Island inverters. Each has 2x SPDT switches. Each switch can be configured for one of two levels of SoC, or for "surplus power available", and other functions like "on grid", "start generator", etc.

I have one wired to a 100A DPST relay, which sheds the entire house at 70% DoD.
I could use one for HVAC thermostat at 20% DoD, another for a dump load.

There are stand-alone SoC based controllers or battery voltage controllers. Not sure which are best for those newfangled LiFePO4 batteries.

What I really want is a frequency-controlled variable load. In an AC coupled system that could harvest exactly the surplus power, use it for heating or variable speed pumping.

 

[zanydroid]

@zanydroid - But if I had a 125A main breaker, I'd need a 125A transfer switch right? I can't find any 125A transfer switches anywhere - maybe they don't make them? Looks like I'd have to go up to a 200A switch...

Yes you would. But you would need a 100A to 125A service upgrade from POCO to justify going to 125A breaker/transfer switch in a location that needs it. Maybe I missed that part of the project scope.

Also you could go to 200A on service, have 100A to solar with bypass and existing loads, and put huge things that don’t need backup upstream of the 100A portion. As I said, MidNite seems to have a lot of system diagrams in mind justifying their 100A design target.